The present invention relates to the releasing of glazing panels from supporting frames, and more specifically to the releasing of laminated glazing panels from supporting frames (such as laminated vehicle windscreens or architectural window panes).
Reference to glazing panels should be understood to mean panels, screens, or windows of glass, plastics or any other material substantially transparent to wavelengths in the visible range of the spectrum.
Vehicle windscreens typically comprise a laminated panel structure comprising an outer glass layer, an inner glass layer and an interlayer, interposed between the outer and inner glass layers. The interlayer typically comprises a material transparent to some wavelengths of visible light but absorbent to ultraviolet radiation (U.V). (In some circumstances the inter layer may be absorbent to some wavelengths of visible light and also typically some infra red radiation.) The inter layer is typically tinted to absorb specific wavelengths (particularly U.V.).
WO-A-9617737 discloses a method and apparatus for releasing bonded transparent screens (typically vehicle windscreens) from supporting frames to which they are bonded. An improved technique has now been devised.
According to a first aspect, the invention provides a method of releasing a glazing panel from a frame to which the panel is bonded by interposed bonding material, the method comprising:
i) arranging light energy delivery means adjacent the glazing panel; and,
ii) operating the light energy delivery means to transmit light energy through the screen to effect release of the panel from the frame.
According to a second aspect the invention provides apparatus for releasing a glazing panel from a frame to which the panel is bonded by interposed bonding material, the apparatus comprising light energy delivery means arrangeable adjacent the glazing panel, and operable to transmit light energy through the screen to effect release of the panel from the frame.
The light energy delivered is preferably of a wavelength substantially in the range 300 nm-1500 nm (more preferably in the range 400 nm-700 nm).
The light energy delivered is desirably pulsed according to a predetermined regime, preferably such that the pulse duration (T on) is less than the inter-pulse interval (T off).
Desirably, a single pulse of light energy delivered is of sufficient energy to effect separation of the screen from the frame along a length of the bonding material.
The apparatus preferably includes a pulse forming network (which may include a capacitor and inductor arrangement) to drive the apparatus to produce a light pulse. The apparatus preferably further comprises a trigger network for initiating operation of the pulse forming network.
Control means is preferably provided for controlling one or more apparatus parameters including the minimum permissible time elapsing between subsequent light pulses. The control means is therefore preferably linked to the trigger network and/or the pulse forming network.
It is preferred that means is provided for selectively adjusting the intensity of the light delivered. This is important in view of the differing degree to which various tinted glazing panels absorb light energy in the wavelength range contemplated. It is preferred that the apparatus includes different preset parameter settings which may be switched dependent upon the glazing panel tint to be de-bonded.
The light energy may be absorbed at the bonding material/panel interface either by the bonding material itself, or by an absorbing layer comprising the panel (such as the frit layer commonly found on vehicle glazing panels) or by a suitable light absorbent coating provided at the interface.
The light energy delivery means may be tracked about the periphery of the panel, preferably at a predetermined rate dependent upon the power of the light energy delivery means and the pulse regime. Advantageously tracking means (preferably motorised tracking means) is provided for this purpose.
Alternatively, the light energy delivery means may be hand held and positioned on the glazing manually by an operator. The delivery means may therefore have a manual trigger for initiating a light pulse when the delivery head is positioned to the operators satisfaction.
In one embodiment, the light energy delivered comprises a plurality of wavelengths, most preferably in the visible range of the spectrum. In one embodiment it is preferred that the light energy is non-coherent. The light energy preferably attenuates rapidly with distance such that at a few centimeters (prefeably less than 10 cm, more preferably less than 5 cm) from the energy delivery means the light energy density is significantly diminished from its maximum value (preferably falling to 50% maximum value or below). The pulse repetition frequency (defining T off) is beneficially substantially in the range 0.1 Hz-10 Hz (most preferably substantially in the range 0.3 Hz-1 Hz). The energy delivered is preferably substantially in the range 100 Joules-10,000 Joules per pulse (more preferably in the range 500-1500 Joules per pulse). The pulse duration (T on) is preferably substantially in the range 1 xcexcs-100 ms, more preferably 1 ms-2 ms.
In a preferred embodiment, the energy delivery means comprises electrical gas discharge apparatus. Desirably, operation of the gas discharge apparatus is controlled to limit the pulse rate and/or duration of the light pulse. The operation of the gas discharge apparatus is preferably controlled by:
i) charging a capacitor arrangement;
ii) initiating a trigger pulse to discharge the capacitor arrangement; and,
iii) discharging the capacitor arrangement through an inductor to the gas discharge apparatus.
Accordingly, for this preferred embodiment, apparatus according to the invention includes energy delivery means comprising electrical gas discharge apparatus.
The electrical gas discharge apparatus is controlled to limit the pulse rate of the light delivered. The apparatus preferably includes a pulse forming network having a capacitor and inductor arrangement in which the capacitor discharges through the inductor to drive the electrical gas discharge apparatus to produce a light pulse. The apparatus preferably further comprises a trigger network for initiating the capacitor of the pulse forming network to discharge.
Control means is preferably provided for controlling one or more apparatus parameters including the minimum permissible time elapsing between subsequent discharge pulses of the electrical gas discharge apparatus.
The electrical gas discharge apparatus preferably comprises an electrical gas discharge tube.
The electrical gas discharge apparatus desirably comprises a reflector (preferably a parabolic reflector) arranged to direct emitted light in a predetermined direction.
The apparatus preferably includes a window through which emmited light is directed to pass through the glazing panel.
In an alternative embodiment, the energy delivery means comprises laser energy delivery means operated to transmit laser radiation through the panel to effect release of the glazing panel from the frame, the laser being operated in quasi continuous wave mode in which a series of discrete pulses of radiation are transmitted.
The pulse regime for the laser is preferably such that the pulse duration (T on) is substantially in the range 100 xcexcs-10 ms and the inter-pulse interval (T off) substantially in the range 100 xcexcs-10 ms.
In a preferred embodiment, the average laser power is 60 W-150 Wxc2x110% (typical peak power 600 Wxc2x120%); the laser tracking speed is preferably in the range 12 mm/Sxc2x120%.
In either embodiment, the apparatus may comprise focussing means arranged to focus the light energy at a predetermined location. For laser delivery means the laser radiation may be focussed to a line, preferably having a line width substantially in the range 200-800 xcexcm (preferably substantially 600 xcexcmxc2x120%). Advantageously the line length is substantially in the range 10 mmxc2x120%. Where a greater line length is required a composite line comprising a plurality of focussed lines may be generated and arranged in end to end relationship. It is believed that the use of laser radiation focussed to a line for the purpose of releasing a glazing panel from a screen is novel and inventive per se.
Desirably, the tracking and quasi-continuous pulsed operation of the laser delivery means is coordinated such that the focussed line moves transversely to its longitudinal direction (that is the line moves in the direction of its width) at a rate such that subsequent pulses of the focussed line overlap. Preferably the degree of linewidth overlap of subsequent pulses is substantially 50% or above (more preferably substantially 80% or above). Operation in this manner ensures good separation of the panel from the frame at the bonding material/panel inner layer interface.
It is preferred that the laser energy delivery means comprises a plurality of laser sources, advantageously arranged in one or more arrays. The laser energy delivery means preferably comprises laser diode means.
It has been found that for laminated screens or panels comprising a tinted interlayer in particular, operation of the light energy delivery means in pulsed mode according to the pulsing regime defined herein (quasi continuous wave mode for the laser delivery means embodiment), provides enhanced results, because energy absorption in the body of the screen or panel, particularly at the interlayer, is minimised.
The invention will now be further described in specific embodiments by way of example only and with reference to the accompanying drawings.